The present invention relates to a compression-bond-connection substrate to be connected to other members by compression-bonding method. The invention also relates to a liquid crystal device comprised of the compression-bond-connection substrate. Also, the invention relates to an electronic equipment comprised of the liquid crystal device.
Currently, liquid crystal devices are being widely used in various types of electronic equipment, such as portable telephones and portable information terminals. In most of these devices, liquid crystal devices are used to display visual information including characters, numbers, and graphical patterns.
The liquid crystal devices are generally comprised of substrates opposing each other and a liquid crystal sealed between the substrates. In the liquid crystal devices, there is a case in which a compression-bond-connection substrate is connected to either one or both of the substrates. The compression-bond-connection substrate has a drive circuit for driving the liquid crystal device. In the drive circuit, elements including IC chips and passive-element chip parts are mounted, and wiring patterns required to connect the abovementioned elements are formed. Also, substrate-side terminals to be conductively connected to terminals on the side of the liquid crystal device are formed at appropriate locations on the compression-bond-connection substrate.
Compression-bonding processing conductively connects substrate-side terminals formed on the compression-bond-connection substrate to terminals formed on the substrates of the liquid crystal device (that is, opposing-side terminals). The compression-bonding processing uses an anisotropic conductive adhesive, such as an ACF (anisotropic conductive film), an ACP (anisotropic conductive paste), or an ACA (anisotropic conductive adhesive). The processing is performed in such a manner that the anisotropic conductive adhesive is sandwiched between the substrate of the liquid crystal device and the compression-bond-connection substrate, and the adhesive is then heated and pressed by using a compression-bonding tool.
As compression-bond-connection substrates, a single-sided wired type, a double-sided wired type, and a multilayer wired type can be considered. The single-sided wired type is a wiring type in which all elements, such as the drive circuit, wiring patterns, and substrate-side terminals are formed on a single side of the substrate. The double-sided wired type is a wiring type in which elements such as the drive circuit, wiring patterns, and substrate-side terminals are arranged on both sides of the substrate, and they become conductive through conductive throughholes as required. The multilayer wired type is a wiring type in which a wiring layer is repeatedly layered with an insulating layer therebetween, and individual wiring layers become conductive through conductive throughholes as required.
FIG. 10 shows a state in which an ACF 59 is used to connect a compression-bond-connection substrate 53 of the double-sided wired type to a compression-bonding target object 52 by compression-bonding. In the state shown, a compression-bonding tool 55 heats the ACF 59 arranged between the compression-bonding target object 52 and the compression-bond-connection substrate 53 at a predetermined temperature and concurrently presses it with a pressure F. The ACF 59 is then caused to harden, resulting in compression-bonding of the compression-bonding target object 52 and the compression-bond-connection substrate 53. By compression-bonding, a plurality of front-side terminals 54 (substrate-side terminals) formed on the compression-bond-connection substrate 53 are individually electrically conductively connected to opposing-side terminals 56 of the compression-bonding target object 52 via conductive balls 62 in the ACF 59.
In the case of the aforementioned conventional compression-bond-connection substrate 53 of the double-sided wired type, however, while the front-side terminals 54 are formed on the compression-bonding side surface, backside terminals 58 are formed on the reverse side of the compression-bonding-side surface. Conventionally, as shown in FIG. 9, the backside terminals 58 are formed parallel to the front-side terminals 54. Also, for example, when the backside terminals 58 are used as an elastic connector such as a rubber connector, the pitch thereof is larger than that of the front-side terminals 54. Therefore, the plurality of front-side terminals 54 includes both types of front-side terminals 54a overlapping with the backside terminals 58 and front-side terminals 54b not overlapping with the backside terminals 58.
In the case of the compression-bond-connection substrate 53 as described above, when compression-bonding is carried out by using the compression-bonding tool 55, a high pressure is exerted on the front-side terminals 54a overlapping with the backside terminals 58 whereas an insufficient pressure is exerted on the front-side terminals 54b not overlapping with the backside terminals 58. This causes the connection between the plurality of opposing-side terminals 56 and the plurality of front-side terminals 54 to be partially insufficient, significantly reducing the reliability of the connection therebetween.
A connection assembly as shown in FIG. 10 uses the compression-bond-connection substrate 53 of the double-sided wired type having a configuration in which the wiring layers are formed on both the front side and the backside of the substrate. Nevertheless, a problem similar to the above arises even in a compression-bond-connection substrate of the multilayer wired type having a configuration in which multiple wiring layers are overlaid.
The present invention is to provide a compression-bond-connection substrate such as that of a double-sided wired type or multilayer wired type that has a configuration in which multiple wiring layers are overlaid and terminals are formed overlappingly in identical regions of both the front surface and the backside surface, which allows stable provision of a highly reliable compression-bonding connected assembly.
The present invention provides a compression-bond-connection substrate to be connected by compression-bonding to a compression-bonding target object provided with opposing-side terminals, including front-side terminals conductively connected to the opposing-side terminals and backside terminals formed at the backsides of the front-side terminals, characterized in that the backside terminals are arranged so as to cross with the front-side terminals.
In such a present invention as above, as shown in FIG. 3 for example, backside terminals 8 formed on the backside of a compression-bond-connection substrate 3 are arranged so as to cross with front-side terminals 4 formed on a compression-bonding-side surface of the substrate 3. As a result, as is apparent in FIG. 3, even when pitch P2 of the backside terminals 8 is larger than pitch P1 of the front-side terminals 4, a portion of the backside terminals 8 is ensured to exist at the backsides of all the front-side terminals 4.
Because of the above, as shown in FIG. 4, in compression-bonding of the compression-bond-connection substrate 3 to a compression-bonding target object 2 by use of a compression-bonding tool 5, the pressure is applied uniformly by the compression-bonding tool 5 to each individual front-side terminals 4. As a result, all the individual front-side terminals 4 can be ensured to be conductively connected to all of individual opposing-side terminals 6. That is, according to the compression-bond-connection substrate of the present invention, even in the case of a substrate on which a plurality of wiring patterns is overlaid, as in a double-sided wired type or a multilayer wired type, a highly reliable compression-bonded assembly can be obtained.
Also, in the compression-bond-connection substrate having the above configuration, the backside terminals may be arranged diagonally to the front-side terminals. In this case also, the same effects as those described above can be obtained.
Also, in the compression-bond-connection substrate having the above configuration, the front-side terminals may be conductively connected to transmissive electrodes formed at least on one of a pair of substrates of a liquid crystal panel which includes the pair of substrates opposing each other and a liquid crystal sealed between the substrates.
Also, in the compression-bond-connection substrate having the above configuration, the backside terminals may be conductively connected to an elastic connector. The xe2x80x9celastic connectorxe2x80x9d has a base including terminal materials themselves or terminal materials, which is formed of an elastic material such as a metal spring or rubber, and has a construction in which a residual force of the elastic material serves so as to connect the terminals. Examples that may be used are a rubber connector as shown in FIG. 5 and a spring connector as shown in FIG. 6.
Also, the compression-bond-connection substrate having the above configuration may be conductively connected to the opposing-side terminals via an anisotropic conductive film.
In the present invention as described above, as shown in FIG. 4 for example, an anisotropic conductive film (ACF) 29 as an adhesive material is sandwiched between the compression-bond-connection substrate 3 and the compression-bonding target object 2. Furthermore, the ACF 29 is heated, and concurrently, the compression-bond-connection substrate 3 and the compression-bonding target object 2 are pressed together with a force F. At this time, the front-side terminals 4 of the compression-bond-connection substrate 3 are ensured to conductively connect to the opposing-side terminals 6 of the compression-bonding target object 2. This allows a highly reliable compression-bonded assembly to be produced.
Also, the present invention provides a liquid crystal device including a pair of substrates opposing each other, a liquid crystal sealed between the substrates, and a compression-bond-connection substrate compression- connected to at least one of the substrates, characterized in that the compression-bond-connection substrate is as described above.
According to the liquid crystal device, even in the case of a substrate on which a plurality of wiring patterns overlap with each other, as in a double-sided wired type or a multilayer wired type, a highly reliable compression-bonded assembly can be obtained. Therefore, occurrence of display defects due to failed electrical conductivity can be avoided.
Also, the present invention provides an electronic equipment comprised of a liquid crystal device, characterized in that the liquid crystal device is as described above, allowing provision of an electronic equipment in which effects similar to the above can be obtained. As electronic equipments of this type, devices such as portable telephones and portable information terminals can be considered.